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Rub a balloon on your head and it will hang on the wall by itself. Nobody put glue on it. Get a balloon before you start — you can do every bit of this one while you listen.
Blow up a balloon and tie it.
Now rub it on your hair. Back and forth, about ten times. Really rub.
Press it flat on the wall. Let go.
It stays there.
A balloon hanging on a wall by itself does look a bit like a magnet.
So go and get a fridge magnet. Hold it on that same wall and let go.
It falls on the floor.
A magnet needs metal. Your wall does not have any. So whatever is holding the balloon up, it is not the magnet trick.
Here is the other guess: the balloon got sticky. Try that too. Take a second balloon, do not rub it, and press it on the wall. It slides straight down. And when your rubbed balloon does finally come off, the wall is not sticky and neither is the balloon.
The wall did not change. The balloon did — and the only thing you did to it was rub it on your head.
When you rub the balloon on your hair, something moves.
Tiny bits jump off your hair and onto the balloon. They are far too small to see, even up close. There is no light and no noise. But they are there, and now the balloon is carrying a big pile of them.
A balloon carrying that pile pulls. It pulls on the wall, and it holds on tight enough to hang there.
You can feel the same pull on your own head. Rub the balloon again, then hold it a little way above your hair and stay still. Your hair stands up and reaches for it.
Rubbing loads the balloon up with something invisible, and a loaded balloon pulls on things near it.
Go one at a time. Press the button, do that one, then come back for the next.
Your fridge magnet fell off the wall. Your rubbed balloon stayed up on the very same wall. So what is holding the balloon there?
Put each one where you think it belongs. If you have a balloon in your hand, go and check any you are not sure about.
Tap an item, then tap where it belongs
You rub the balloon on your hair again. Then you hold it still, a little way above your head. Your hair rises up and reaches towards it. Why?
You’re previewing as a parent — nothing here is recorded.
That’s the last one in this channel for now. More are on the way.
Back to all episodesRubbing two different materials together transfers electric charge from one to the other — electrons move from the hair to the rubber balloon, leaving the balloon negatively charged and the hair positively charged. This is the triboelectric effect (Encyclopaedia Britannica, 'static electricity'; American Chemical Society, 'Static Electricity' classroom activity). A charged balloon sticks to a wall by polarisation, not magnetism: the balloon's charge pushes like charges in the wall's surface slightly away and pulls unlike charges slightly closer, and that small difference produces a net attraction. The wall itself is uncharged before and after (US Department of Energy Office of Science, 'Ask a Scientist'; Britannica, 'electrostatics'). Magnetic attraction requires ferromagnetic material — iron, nickel, cobalt — which ordinary painted plaster or plasterboard does not contain. This is why a fridge magnet falls off the same wall a charged balloon hangs on (Britannica, 'magnetism'). Static charge dissipates faster in humid air because water molecules in the air carry charge away from the surface; this is the standard explanation for static effects being far weaker on damp days and in steamy rooms (National Institute of Standards and Technology, electrostatics guidance; American Chemical Society). Hair rises towards a charged balloon by the same attraction, and separate hairs carrying the same charge push each other apart, which is why hair also spreads out (American Chemical Society, 'Static Electricity').